225/40R17 vs 245/35R17
Going from one to the other changes the overall height by -1.4 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 225/40R17 | 245/35R17 | Change |
|---|---|---|---|
| Overall height | 24.1" | 23.8" | -1.4 % |
| Sidewall | 3.54" | 3.38" | -4.7 % |
| Section width | 225 mm | 245 mm | +8.9 % |
| Circumference | 75.7" | 74.6" | -1.4 % |
| Revs per mile | 837 | 849 | +1.4 % |
| Axle height | 12.04" | 11.88" | -4.3 mm |
| Approved rim width | 6–8.5" | 7–9" | overlap 7–8.5" |
Both are approved on a rim 7" to 8.5" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 225/40R17. Fit 245/35R17 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.6 mph | -0.4 |
| 50 mph | 49.3 mph | -0.7 |
| 70 mph | 69.0 mph | -1.0 |
| 90 mph | 88.7 mph | -1.3 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,861 on the road, so it over-counts by 139. At a true 70 mph the first turns 977 times a minute, the second 991.